Retaining means for initial thread ends and thread cutting device for double chainstitch sewing machines

ABSTRACT

Simplified means for chainstitch sewing machines for retaining a relatively short initial thread end depending from the eye of the looper, and clamping means for the initial thread end of the needle thread for assuring that, after beginning of sewing, this initial thread end is positively at the bottom surface of the workpiece and has a short length. A thread cutting device provided with said means, in connection with a double chainstitch sewing machine having a thread carrying looper which is moved along a substantially elliptical path encircling the needle and causes a cutting off of the needle thread and the looper thread below the workpiece after is formed. When the sewing is resumed the initial thread ends are controlled in such a manner, that these also remain positively at the bottom surface of the workpiece, while in both cases the thread ends protruding from the workpiece, have a relatively short length. Substantially, the simplified means for retaining the initial thread end consists of a small brush which cooperates with the thread carrying looper and with a thread-guarding groove located in the rear face of the looper blade in certain positions of the looper.

United States Patent Heimann et al.

[ 1 Sept. 5, 1972 [54] RETAINING MEANS FOR INITIAL THREAD ENDS AND THREAD CUTTING DEVICE FOR DOUBLE CHAINSTITCH SEWING MACHINES [72] Inventors Alfred Heimann, Senne; Horst Thiele, Ubbedisse; Horst Meyer, Schotmar, all of Germany [73] Assignee: Kochs Adlemghmaschinen Werke AG, Bielefeld, Germany [22] Filed: March 19, 1971 [21] App]. N0.: 125,960

521 US. (:1. ..112/252, 112/253, 112/200 51 Int. Cl. ..D05b 65/02 [58] Field of Search ..112/252, 253, 197, 199, 200

[56] References Cited UNITED STATES PATENTS 1,816,308 7/1931 Allen ..112/252 1,883,654 10/1932 Ericsson ..112/252 2,334,569 11/1943 Lyons ..112/253 x 3,354,852 11/1967 Kennedy et a1 ..112/252 3,371,633 3/1968 Hedgegaard ..112/252 3,424,117 1/1969 Schopf ..1 12/252 3,425,370 2/1969 Stames ..112/252 x 3,599,588 8/1971 Angele ..112/252 Primary Examiner-James R. Boler Attorney-Jacob L. Kollin [57] ABSTRACT Simplified means for chainstitch sewing machines for retaining a relatively short initial thread end depending from the eye of the looper, and clamping means for the initial thread end of the needle thread for assuring that, after beginning of sewing, this initial thread end is positively at the bottom surface of the workpiece and has a short length.

A thread cutting device provided with said means, in connection with a double chainstitch sewing machine having a thread carrying looper which is moved along a substantially elliptical path encircling the needle and causes a cutting off of the needle thread and the looper thread below the workpiece after is formed. When the sewing is resumed the initial thread ends are controlled in such a manner, that these also remain positively at the bottom surface of the workpiece, while in both cases the thread ends protruding from the workpiece, have a relatively short length.

Substantially, the simplified means for retaining the initial thread end consists of a small brush which cooperates with the thread carrying looper and with a thread-guarding groove located in the rear face of the looper blade in certain positions of the looper.

9 Claims, 13 Drawing Figures RETAINING MEANS FOR INITIAL THREAD ENDS AND THREAD CUTTING DEVICE FOR DOUBLE CHAINSTITCH SEWING MACHINES BACKGROUND OF THE INVENTION This invention relates to means for retaining the initial thread ends depending from the eyes of the needle and the thread carrying looper of a double chainstitch sewing machine having a thread cutting device, said machine being provided with these retaining means.

When stitching seams it is often desired to terminate the latter within the workpiece, in which the needle thread and looper thread are to be cut off below the workpiece with a minimum projecting length from the workpiece and at the start of a renewed sewing cycle, the initial thread ends likewise have to remain below the material.

Prior to the beginning of a scam the initial thread end depending from the needles eye, and the thread carrying looper must be of a sufficient length, in order to prevent unthreading of the threads during the first stitch of the needle. However, on the other hand, the thread ends should not be too long, so as to draw the initial thread end of the needle thread safely downwards through the workpiece after the first stitch of the needle, in order to accomplish the demand for initial thread ends projecting from the material while having a length as short as possible.

There is already known a double chainstitch sewing machine for attaching buttons, which is provided with a device for clamping and subsequently cutting off the needle thread and looper thread by means of a stationary cutting blade having an elastic clamping member, and a thread engaging and clamping member moving across the path of the needle, to engage the looper, and to carry both to the elastic clamping member. Such a device is disclosed in US. Pat. No. 1,883,654.

In this known thread cutting device the thread end between the looper eye and the thread clamp, is clamped until the next stitch is formed. Likewise, the end of the shank extending about the looper and running through the workpiece to the needles eye, is clamped until the workpiece is withdrawn at which time the loosened needle thread, delivered by a thread pulling device prior to the stoppage of the machine, is drawn through the needles eye prior to the releasing of the needle thread from the clamp. Thus, a sufficient length of the needle thread is available for forming the next stitch.

In order to initiate a proper stitch formation with the first stitch of the needle, the thread extending from the needles eye must be of such length that the thread end will not be drawn through the workpiece during the first penetration of the needle. However, when using the above mentioned or similar known thread cutting devices in connection with a double chain-stitch sewing machine, and which have no means for disposing the initial thread end of the needle thread below the workpiece underface, it becomes necessary to subsequently cut off the thread end of the needle thread located above the workpieces upper face by means of a scissor, immediately after the first stitch of the needle, in order to achieve a proper seam.

US. Pat. No. 3,371,633 discloses a thread withdrawing and cutting device for use with a double chainstitch sewing machine having a thread carrying looptaker hook operable in a composite movement about a pair of axes at a right angle to one another, for effecting both the needle loop seizing and casting off movements, as well as avoiding needle looptaker movements. in this known thread withdrawing and cutting device, the shaft or spindle forming one of the oscillating axles of the looptaker operating mechanism, is movably mounted and operably connected with the transmission or control device of the thread cutter. The looptaker is displaced during a thread withdrawing and cutting operation from a normal sewing position in such a manner as to withdraw a sufficient length of looper and needle thread, while providing adequate space for the proper mounting of the cutting device.

However, there are disclosed no means for clamping the needle and looper threads prior to or after their cutting off, so that with regard to the primary require ment of a safe stitch formation with the beginning of a seam, a longer thread amount must be drawn off than effectively required for the renewed stitch formation. Moreover, there are provided means for drawing off different thread lengths independent of one another, so that the ends of the needle thread and looper thread projecting from the workpiece will be of different lengths.

Finally, there is known a thread severing device for severing the looper and needle threads on double chainstitch sewing machines, in which is provided a thread seizing device or thread catcher which moves between the looper blade and the stitching plate, and cooperates with a cutting blade and a flat clamping spring, in order to seize and cut off the looper and needle threads in such a position that a proper stitch formation is guaranteed at the beginning of the next seam. This device is disclosed in US. Pat. No. 3,424,l 17.

Besides the usual looper thread take-up operating during each stitch forming cycle, this known thread cutting device is provided with two additional thread pulling members for the looper and needle thread, both of which are usually operated together with the thread catcher when the cutting operation is started means of an electromagnet, in order to draw off an amount of thread from the thread supply, which amount is determined by the length of the path covered by the thread catcher while it is moving into its end position, and to procure a sufficient needle thread amount for a proper initial stitch formation prior to the beginning of the next seam. However, due to the lack of a device for clamping the initial thread end of the needle thread below the stitching plate in the construction of this known thread severing device, it is more or less left to chance, to terminate all of the four thread ends below the workpiece after forming a seam.

The principal object of the present invention is to provide means, for use in double chain stitch sewing machines, which will prevent the eyes of the needle and the looper from withdrawing the relative short initial ends of the sewing threads at the beginning of a seam.

It is-a further object of this invention to provide means for use in connection with a thread cutting device, which will cause the initial thread ends origin ating from the cutting off of the threads, to be on the underface of the workpiece after the renewed beginning of the sewing.

Another object of this invention is to provide a thread cutting device, which is provided with means for preventing the eyes of the needle and the looper from withdrawing of the relative short initial ends, and which is suitable for using in a double chainstitch sewing machine having a thread carrying looper, which is moved along a substantially elliptical path encircling the needle.

A further object of the invention is to provide a device for double chainstitch sewing machines, for cutting the threads and causing all thread ends of a seam to be on the bottom face of a workpiece after forming the seam.

Further objects and advantages of the present invention will become apparent as it is described in detail below with particular reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation, showing a sewing machine frame with a double chainstitch sewing machine embodying the invention, and the driving motor;

FIG. 2 shows detail of FIG. 1 in on an enlarged scale;

FIG. 3 is a partial front elevational view of the sewing machine showing the thread cutting device;

FIG. 4 is a perspective view of the thread cutting device;

FIG. 5 is a sectional view taken along line V-V of FIG. 3;.

FIG. 6 is a sectional view taken along line VI-VI of FIG. 3; I

FIG. shows the thread-seizing cutting knives immediately prior to the cutting off of the threads, and the clamping means for the looper thread;

FIG. 8 is a top plan view of the looper, showing the positions of the threads after removal of the workpiece;

FIG. 9 shows the position of the looper shortly after the first forward movement following the beginning of the sewing operation;

FIG. 10 shows the clamping of the needle thread drawn through the workpiece after the first stitch of the needle;

FIG. 11 is a partial perspective view of the looper and the needle according to FIG. 10;

FIG. 12 shows the beginning of the first thread interlocking after the commencement of the sewing operation and FIG. 13 shows a part of a seam and the needle and looper thread ends positioned below the workpiece.

As shown in FIG. 1, a sewing machine 2 supported in a frame 1, conventionally comprises a bedplate 3, a standard 4 and an overhanging arm 5 terminating in a head 6. The driving of the sewing machine 2 is effected by means of a stop motor 7 via a belt 8 and a hand wheel 9, on which is arranged a position transmitter 10 cooperating with the motor 7. After the motor 7 is switched off my means of a treadle 11, the position transmitter 10 effects the stopping of the sewing machine 2, at which time the needle 12 is in top position.

A thread carrying double chainstitch looper 13 (FIGS. 3,4) cooperating with the needle 12, is disposed on a looper carrier 14, secured to a rocking shaft 15, which operates the looper 13 about a substantially ellipticalpath in synchronism with the needle 12. The

driving parts for the rocking shaft 15 are accommodated in a looper housing 16 and are driven by the arm shaft of the sewing machine 2 (not shown).

Secured to the bedplate 3 is a throat plate 17 (FIGS. 3,5,7,11,12), which is provided, in the usual manner, with a longitudinal stitch hole 18, for the passage of the needle 12, and slots 19 for the passage of a feed dog 20 (FIG. 3). The four motions of the feed dog 20 are obtained, in a not further described manner, by a driving shaft 21 and a feed shaft (not shown), which is driven by the latter. The driving shaft 21 (FIG. 5) also drives the rotary thread cams 22 (FIGS. 4,7) which serve the purpose of withdrawing the looper thread 23 from the looper 13 when the latter is starting its return movement. Two thread guiding forks 24 provided with eyes 25, are disposed on a shaft 26 (FIG. 4) laterally of the two rotary thread cams 22. The shaft 26 is pivoted in a block 27'secured to the looper housing 16. Clamped upon the shaft 26 in a recess of the block 27 is a lever 28, which carries an angled stop plate 29 engaging in a forked part 30.

Screwed to the looper housing 16 (FIGS. 3 and 4) is a bearing block 31, adapted for swingably bearing a knife carrier 32. For this purpose, there is pivoted in the bearing block 31' a shaft 33, to which are secured two guide levers 34. The free ends of said guide levers 34 are clamped to a rod 35 pivoted in the knife carrier 32 and secured against axial displacement by means of adjusting rings 36. A guide lever 38, provided with lugs 37, is rotatably received with its one end in a bearing eye 39 of the bearing block 31; the other end is pinjointed in a bearing 40 in the knife carrier 32, to which the lug 37 is secured against axial displacement in a not further shown manner.

Arranged upon an inclined plane 41 of the knife carrier 32 is a scissor-shaped thread cutter 42 consisting of a counterknife 43, a cutting blade 44 rotatably secured to the latter, a spring 45 and an eccentric screw 46. The counterknife 42 terminating in a point-like projection 47 and formed with a cutting edge 48 (FIGS. 4,8), is secured to the knife carrier 32 by means of screw 49. The cutting blade 44, movably connected with the counterknife 43 by means of a rivet 50, is formed with a nose 51 and a lateral arm 52, against which abuts the spring 45. The other end of the spring 45 is secured to the counterknife 43 by means of a screw 49. The nose 51 rests against the eccentric screw 46 under the tension of the spring 45. The opening between the two knives 44, 43 is adjustable by means of said screw 46.

Pivoted about a lug 54 on the bearing block 31 is a double armed connecting lever 53. One arm 56 of the lever 53, formed with a fork 55, embraces the projecting part of the rod 35, while the other offset arm 57 carries at its end a lug 58. Furthermore, a lever 59 is hinged to the arm 57 by means of a lug 60. The lever 59 is provided with an oblong hold 61. A flange screw 62 extends therethrough and is inserted in an arm 63 of the bearing block 31. At its free end the lever 59 is formed with a recess 64, in which can engage a circular disk 65, as shown in FIG. 2, when the sewing machine 2 is inserted in the frame 1. The disk 65 is axially displaceably supported on an extension piece 66, which is disposed on the armature 67 of an electromagnet 68 secured to the frame 1 (FIG. 1). The lever 59 is under the tension of a spring 69 engaging with an eye 70,

secured to the looper housing 16, and a pin 71 inserted in the lever 59 (FIG. 4).

About a lug 72 inserted in the bedplate 3, is pivoteda double-armed lever 73 (FIGS. 3 to 6), one arm of which is formed with a nose 75 for cooperation with a cam 76 fixedly clamped upon the driving shaft 21. To the other arm 78 of the double-armed lever 73, tensioned by a torsion spring 77, is articulated a forked piece 79 formed with a lug 80, to which a thread clamping carrier 81 is clampably secured. Screwed to the thread clamping carrier 81 by means of a screw 82 is a needle thread clamping plate 83 having a recess 84 for the passage of the needle 12, and forwardly a clamping face 85.

The clamping face 85 of the thread clamping plate 83 is pressed under the tension of the spring 86 (FIG. 4) against the throat plate 17. One end of the spring 86 engages in the forked piece 79, while the other end engages in a bore (not shown) of an adjusting screw 88 inserted in a lug 87.

A L-shaped arresting plate 89 is secured to the arm 74 of the lever 73 by means of screws 90 and formed with a cutout 91. At its end, the arresting plate 89 carries a screw bolt 92, which is screwably inserted therein and secured by a nut 93.

Pivoted about a bolt 94 vertically inserted in the bedplate 3, is a notched plate 95, which'is under the tension of a torsion spring 96 and serves to lock the arresting plate 89. Below a part 97 angled about 45 toward the bottom, is bolted a spring plate 98, the free end of which projects from the part 97 and lies in the path of motion of the lug 58 carried by the offset arm 57. The notched plate 95 touches with its angled part 99 behind the cutout 91 of the arresting plate 89.

Pivoted on a bolt 100 horizontally disposed in the bedplate 3, is a looper thread clamping lever 101, one arm 102 of which is provided with a tongue 103, while the other arm 104 carries at its end a plastic or rubber bushing 105.

A movable angle plate 106 is bolted together with the arresting plate 89 (FIGS. 3 to 5 and 7) to the lever 28 by means of screws 107. To the angled side of the angle plate 106 is swingably secured a looper thread clamping plate 108 about a collar screw 109. A pin 110 disposed in the angle plate 106 and projecting through a clearance 1 l 1 of the thread clamping plate 108, limits the sweep. The looper thread clamping plate 108 is formed in front with a bearing surface 112, against which the looper thread 23 (FIG. 7) extending through an opening 1 13 in the angle plate 106, can rest.

In the known manner, the double chainstitch looper 13 has, in front, a thread guiding groove 114 and on the opposite side of the looper blade a thread guarding groove 115 (FIG. 8). Disposed in the path of motion of the looper 13 is a brush 116, the bristles 117 of which abut against the looper 13 during the forward motion of the latter, in the thread guarding groove 115 (FIGS. 4 and 8).

Secured to the bearing block 31 (FIG. 4) by means of screws 118 is a stop member 117', the upper end of which lies in the path of motion of the arm 52 of the cutting blade 44.

The operation of the thread cutting device is as f0llows:

After a seam is terminated and after the treadle 11, is released the needle 12 is caused by means of the stop motor 7, to automatically reach its top position. Now, when the treadle 11 is pressed into the opposite direction, the magnet 68 is energized by means of a contact in the motor 7 (not shown). The lever 59 is drawn to the left by means of the disk 65 (FIG. 2), and the double armed lever 53 is moved thereby about the lug 54 (FIGS. 3,4), while the knife carrier 32, swingable about the shaft 33 and the lug 37, carries the thread cutter 42 to the stitch forming place, shown in FIG. 7. After the looper thread 23 has been already seized by the two knives 43, 44, the point 47 of the counterknife 43 arrives between the shank extending to the workpiece, and the shank of the needle thread loop located on the looper and extending to the needle. If now the thread cutter 42 is moved on, the lateral arm 52 of the cutting blade 44 will rest against the stop 117', so that the cutter is closed and the shank of the needle thread loop formed by the needle thread 119 and extending to the workpiece, as wellas the looper thread 23 are cut off. After this, the workpiece 120 can be removed with all thread ends located on its underface. After cutting off the threads 23, 119, the knife carrier 32 assisted by the spring 69, is returned into its initial position (FIG. 4).

During the forward movement of the thread cutter 42, the lug 58 disposed on the offset arm 57, has been moved downwards and has pressed aside the spring plate 98 arranged on the notched plate 95 (FIGS. 5,6), during the time of its passage, without moving the notched plate 95. When the knife carrier 32 and thus the double armed lever 53 move back, the lug 58 rests also against the transversely arranged spring plate 98, which is now forced to the right into the position, shown in dotted lines in FIG. 6. The angled edge 99 effecting the locking, comes out of engagement with the arresting plate 89, which influenced by the torsion spring 77 (FIG. 5), now moves in such a manner, that the screw bolt 92 rests against the tongue 103 of the looper thread clamping lever 101 and moves the latter against the tension of the torsion spring 121, so that its arm 104, covered with a bushing 105 (FIG 7), presses the looper thread 23 against the bearing surface 112 of the thread clamping plate 108. Thereby, and due to the thread 23 is prevented from being drawn out of the looper eye with the beginning of a new sewing cycle, but retains a length as shown in FIG. 8. This FIGURE shows also, that in consequence of the movement of the double armed lever 73, the thread clamping plate 83 has been drawn forwards, so that its clamping face 85 is no longer positioned against the throat plate 17 (FIG. 7) behind the needle. Due to the release of the double armed lever 73 by means of the notched plate 95, the nose (FIGS. 5,7) moves into the base circle of the cam 76.

With the beginning of a new seam, the needle 12 pierces the workpiece 120, while the initial thread end depending from the eye of the needle 12, remains beneath the throat plate 17 when the needle moves into its top position. Now, when the cam 76 is in active connection with the nose 75, the double armed lever 73 is moved against the tension of the torsion spring 77. Consequently the end of the needle thread 1 19 is seized by the clamping face of the thread clamping plate 83 and clamped between the latter and the part of the throat plate behind the needle, as shown in FIGS. and 11.

With the movement of the double armed lever 73 caused by the cam 76, the bearing edge 91a of the cutout 91 which till now rested against the beveling of the angled edge 99, moves in front of the angled edge 99 (FIGS. 4 and 6) tensioned by the torsion spring 96, and remains there until the magnet 68 is energized again.

During the first stitch of the needle 12 and during its return movement, the looper 13 has trailed the projecting thread end 23, while the looper thread clamp (105, 112) was closed. Now, when the looper 13 is moving ahead, as shown in FIG. 9, the looper thread end 23 is seized by the brush 116, 117 and placed into the thread guarding groove 115 (FIG. 10), and the thread drawn off from the thread supply by means of the rotary thread earns 22, is partly trailed, while the thread clamp 105, 112 is opened. Upon the renewed forward movement of the looper 13, the first needle thread loop is formed, while the looper thread 23 is now positioned between the needle thread shank extending to the workpiece, and the looper 13. FIG. 12 shows, that with the return of the looper 13 the needle 12 can enter the loop formed by the looper thread 23. Thereupon, the needle thread loop carrying the end of the looper thread 23 upwards beneath the workpiece 120, can be cast off. The next stitch formation takes place in the usual manner (FIGS. 12,13).

What we claim is:

1. In a chainstitch sewing machine provided with a reciprocating thread carrying needle, a thread carrying looper having a blade formed with a transverse eye for delivering thread from one side of said blade to the other side, a thread guiding groove in the front face of said blade and ending in said eye, the rear face of said blade having a thread guarding groove, means for operating said looper along a substantially elliptical path encircling said needle, a looper thread take-up mechanism, means for preventing said eye from withdrawing a relatively short initial end of said looper thread by said looper thread take-up mechanism after a renewed beginning of sewing, said means including a looper thread clamping means located between said looper and said looper thread take-up mechanism, and a brush cooperating with said rear face of said looper blade for guiding said initial end of said looper thread depending from said looper eye into said thread guarding groove during the first forward motion of said looper after a renewed beginning of sewing.

2. In combination with a chainstitch sewing machine provided with a reciprocating thread carrying needle, a throat plate, a Looper housing, a thread carrying oscillating looper having a blade formed with a transverse eye for delivering thread from one side of said blade to the other side of a thread-guiding groove in the front face of said blade and ending in said eye and a threadguarding groove in the rear face of said blade, means for operating said looper along a substantially elliptical path encircling said needle, and a looper thread takeup mechanism, a thread cutting means for cutting said looper thread and the shank of the needle thread loop extending to the workpiece below said throat plate, comprising thread catching and cutting means, means for actuating said thread catching and cutting means in dependence of the position of said needle, looper thread clamping means being effective during the cutting process and ineffective after beginning a new seam and prior to the beginning of the second stitch of said needle, for preventing said looper eye from withdrawing said looper thread by said looper thread take-up mechanism, means for clamping the initial end of said needle thread below said throat plate after forming the first stitch, a brush cooperating with said rear face of said looper blade for guiding the end of said looper thread depending from said looper eye into said thread-guarding groove after a cutting cycle, thereby withdrawing a quantity of thread made ready by said looper thread take-up mechanism, through said looper eye caused by the first motion of said looper behind said needle after a renewed beginning of sewing, and actuating means for said looper thread clamping means and said means for clamping the initial end of said needle thread.

3. The combination as claimed in claim 2, wherein said looper thread clamping means is mounted between said thread carrying looper and said looper thread takeup mechanism.

4. The combination as claimed in claim 2, wherein said thread cutting device further comprises a knife carrier carrying said catching and cutting means, said means consisting of a fixed counterknife having a cutting edge and a point-like projection, a movable cutting blade cooperating with said counterknife and formed with a lateral arm, a spring for holding said knives in an opened position, guide levers to hinge said knife carrier to said looper housing, a'stop means situated in the path of motion of said lateral arm for actu ating said cutting blade after diverting said knife carrier in the direction of said looper in workpiece, and to separate and out said threads extending to the workpiece,and a lever arrangement connected with said actuating means and said knife carrier, for controlling said clamping means in dependence of the position of said thread catching and cutting means.

5. The combination as claimed in claim 2, wherein said means for clamping the initial end of said needle thread below said throat plate after forming the first stitch comprises a thread clamping plate cooperating with a part of said throat plate, said part being behind said needle, means for moving said thread clamping plate from said position in front of said needle into said position behind said needle during the exit of said needle from said throat plate after forming the first stitch in order to engage and clamp said initial end of said needle thread between said thread clamping plate and said part of said throat plate, and means for holding said thread clamping plate in said position behind said needle during the sewing operation of said chainstitch sewing machine.

6. The combination as claimed in claim 2, wherein said looper thread take-up mechanism comprises two driven slotted rotary thread earns, a cast-off blade situated between said rotary thread earns, a thread guiding fork, a lever connected with said thread guiding fork for deflecting said fork, and having a stop plate for arresting said lever in the operating position, said looper thread clamping means including an angle plate carried by said lever and having an opening for the passage of said looper thread, a looper thread clamping plate formed with a bearing surface for said looper thread and pivoted about a collar screw secured to said angle plate, and further formed with a clearance, a pin within said clearance secured to said angle plate for limiting the rotary motion of said clamping plate, a pivoted tooper thread clamping lever having a first arm carrying a rubber bushing for clamping said looper thread between said bearing surface and said first arm, a second arm formed witha tongue for actuating said looper thread clamping lever by said actuating means, and a spring for holding said looper thread clamping lever in an inoperative position.

7. The combination as claimed in claim 2, wherein said means for clamping the initial end of said needle thread below said throat plate after forming the first stitch comprises a double armed lever pivoted to said sewing machine and formed with a nose, a forked piece linked to one arm of said double armed lever and formed with a lug, a thread clamping plate carried by said thread clamping carrier and having a cutout for forming a clamping face cooperating with a part of said throat plate, said part being behind said needle, a torsion spring between said arm of said double armed lever and said forked piece for pressing said clamping face of said needle thread clamping plate against said throat plate, a spring bearing upon said double armed lever in order to move said clamping face of said clamping plate into a position in front of said needle after accomplishing the cutting operation, a rotary driven cam cooperating said said nose of said doublearmed lever for moving said clamping face from said position in front of said needle into said position behind said needle during the exit of said needle out of said throat plate after forming the first stitch for engaging and clamping said initial end of said needle thread between said clamping face and said part of said throat plate, arresting means for holding said clamping face in said position behind said needle during the sewing operation of said chainstitch sewing machine, and unlocking means cooperating said said actuating means for said thread catching and cutting means in for eliminating the arrest when operating said thread catching and cutting means, said looper thread clamping means being effective during the cutting process and ineffective after the beginning of a new seam and prior to the beginning of the second stitch of said needle, for preventing said looper eye from withdrawing said looper thread by said looper take-up mechanism, mounted between said thread carrying looper and said looper thread takeup mechanism and actuated by said actuating means for said looper thread clamping means.

8. The combination as claimed in claim 2, wherein said means for actuating said thread catching and cutting meanscomprises a stop motor for driving said sewing machine and moving said needle into an upper dead position after terminating the sewing operation, an electromagnet controlable after terminating the sewing operation and when said needle is in said upper dead position, for driving said catching and cutting means, said actuating means for said looper thread clamping means and said device for clamping the initial end of said needle thread including connecting means between said electromagnet driving said catching and cut in eans, said er threa clam in eans and said d i ce for clampin g the init ial end ofis id needle thread, arresting means for said looper thread clamping means and said means for clamping said needle thread, said arresting means being effective during sewing of sewing machine, and unlocking means cooperating with said arresting means for eliminating the arrest when operating said thread catching and cutting means.

9. The combination as claimed in claim 7, wherein said arresting means for holding said clamping face in said position behind said needle during the sewing operation of said chainstitch sewing machine, said unlocking means cooperating with said actuating means for said thread catching and cutting means for eliminating the arrest when operating said thread catching and cutting means comprising an arresting plate secured to the other arm of said double-armed lever and having a cutout with a bearing edge, a notched plate pivoted to said sewing machine and having an angled edge cooperating with said bearing edge of said arresting plate, and a downwardly angled part, a spring plate secured to the underface of said downwardly angled part of said notched plate, a spring for bearing said notched plate against said bearing edge of said arresting plate, a double armed connecting lever, one arm of which being connected with said actuating means for said thread catching and cutting means, a lug secured to the other arm of said double-armed connecting lever and cooperating with said spring plate, said looper thread clamping means including a pivoted looper thread clamping lever having a first arm for clamping said looper thread between a bearing surface and said first arm, and a second arm formed with a tongue, and a spring for holding said looper thread clamping lever in an inoperative position, actuated by said actuating means for said looper thread clamping means and consisting of an adjustable set screw inserted in said arresting plate and cooperating with said tongue of said looper thread clamping lever. 

1. In a chainstitch sewing machine provided with a reciprocating thread carrying needle, a thread carrying looper having a blade formed with a transverse eye for delivering thread from one side of said blade to the other side, a thread guiding groove in the front face of said blade and ending in said eye, the rear face of said blade having a thread guarding groove, means for operating said looper along a substantially elliptical path encircling said needle, a looper thread take-up mechanism, means for preventing said eye from withdrawing a relatively short initial end of said looper thread by said looper thread take-up mechanism after a renewed beginning of sewing, said means including a looper thread clamping means located between said looper and said looper thread take-up mechanism, and a brush cooperating with said rear face of said looper blAde for guiding said initial end of said looper thread depending from said looper eye into said thread guarding groove during the first forward motion of said looper after a renewed beginning of sewing.
 2. In combination with a chainstitch sewing machine provided with a reciprocating thread carrying needle, a throat plate, a Looper housing, a thread carrying oscillating looper having a blade formed with a transverse eye for delivering thread from one side of said blade to the other side of a thread-guiding groove in the front face of said blade and ending in said eye and a thread-guarding groove in the rear face of said blade, means for operating said looper along a substantially elliptical path encircling said needle, and a looper thread take-up mechanism, a thread cutting means for cutting said looper thread and the shank of the needle thread loop extending to the workpiece below said throat plate, comprising thread catching and cutting means, means for actuating said thread catching and cutting means in dependence of the position of said needle, looper thread clamping means being effective during the cutting process and ineffective after beginning a new seam and prior to the beginning of the second stitch of said needle, for preventing said looper eye from withdrawing said looper thread by said looper thread take-up mechanism, means for clamping the initial end of said needle thread below said throat plate after forming the first stitch, a brush cooperating with said rear face of said looper blade for guiding the end of said looper thread depending from said looper eye into said thread-guarding groove after a cutting cycle, thereby withdrawing a quantity of thread made ready by said looper thread take-up mechanism, through said looper eye caused by the first motion of said looper behind said needle after a renewed beginning of sewing, and actuating means for said looper thread clamping means and said means for clamping the initial end of said needle thread.
 3. The combination as claimed in claim 2, wherein said looper thread clamping means is mounted between said thread carrying looper and said looper thread take-up mechanism.
 4. The combination as claimed in claim 2, wherein said thread cutting device further comprises a knife carrier carrying said catching and cutting means, said means consisting of a fixed counterknife having a cutting edge and a point-like projection, a movable cutting blade cooperating with said counterknife and formed with a lateral arm, a spring for holding said knives in an opened position, guide levers to hinge said knife carrier to said looper housing, a stop means situated in the path of motion of said lateral arm for actuating said cutting blade after diverting said knife carrier in the direction of said looper in workpiece, and to separate and cut said threads extending to the workpiece, and a lever arrangement connected with said actuating means and said knife carrier, for controlling said clamping means in dependence of the position of said thread catching and cutting means.
 5. The combination as claimed in claim 2, wherein said means for clamping the initial end of said needle thread below said throat plate after forming the first stitch comprises a thread clamping plate cooperating with a part of said throat plate, said part being behind said needle, means for moving said thread clamping plate from said position in front of said needle into said position behind said needle during the exit of said needle from said throat plate after forming the first stitch in order to engage and clamp said initial end of said needle thread between said thread clamping plate and said part of said throat plate, and means for holding said thread clamping plate in said position behind said needle during the sewing operation of said chainstitch sewing machine.
 6. The combination as claimed in claim 2, wherein said looper thread take-up mechanism comprises two driven slotted rotary thread cams, a cast-off blade situated between said rotary thread cams, a thread guiding fork, a lever connected with said thread guiding fork for deflecting said fork, and having a stop plate for arresting said lever in the operating position, said looper thread clamping means including an angle plate carried by said lever and having an opening for the passage of said looper thread, a looper thread clamping plate formed with a bearing surface for said looper thread and pivoted about a collar screw secured to said angle plate, and further formed with a clearance, a pin within said clearance secured to said angle plate for limiting the rotary motion of said clamping plate, a pivoted tooper thread clamping lever having a first arm carrying a rubber bushing for clamping said looper thread between said bearing surface and said first arm, a second arm formed with a tongue for actuating said looper thread clamping lever by said actuating means, and a spring for holding said looper thread clamping lever in an inoperative position.
 7. The combination as claimed in claim 2, wherein said means for clamping the initial end of said needle thread below said throat plate after forming the first stitch comprises a double armed lever pivoted to said sewing machine and formed with a nose, a forked piece linked to one arm of said double armed lever and formed with a lug, a thread clamping plate carried by said thread clamping carrier and having a cutout for forming a clamping face cooperating with a part of said throat plate, said part being behind said needle, a torsion spring between said arm of said double armed lever and said forked piece for pressing said clamping face of said needle thread clamping plate against said throat plate, a spring bearing upon said double armed lever in order to move said clamping face of said clamping plate into a position in front of said needle after accomplishing the cutting operation, a rotary driven cam cooperating said said nose of said double-armed lever for moving said clamping face from said position in front of said needle into said position behind said needle during the exit of said needle out of said throat plate after forming the first stitch for engaging and clamping said initial end of said needle thread between said clamping face and said part of said throat plate, arresting means for holding said clamping face in said position behind said needle during the sewing operation of said chainstitch sewing machine, and unlocking means cooperating said said actuating means for said thread catching and cutting means in for eliminating the arrest when operating said thread catching and cutting means, said looper thread clamping means being effective during the cutting process and ineffective after the beginning of a new seam and prior to the beginning of the second stitch of said needle, for preventing said looper eye from withdrawing said looper thread by said looper take-up mechanism, mounted between said thread carrying looper and said looper thread takeup mechanism and actuated by said actuating means for said looper thread clamping means.
 8. The combination as claimed in claim 2, wherein said means for actuating said thread catching and cutting means comprises a stop motor for driving said sewing machine and moving said needle into an upper dead position after terminating the sewing operation, an electromagnet controlable after terminating the sewing operation and when said needle is in said upper dead position, for driving said catching and cutting means, said actuating means for said looper thread clamping means and said device for clamping the initial end of said needle thread including connecting means between said electromagnet driving said catching and cutting means, said looper thread clamping means and said device for clamping the initial end of said needle thread, arresting means for said looper thread clamping means and said means for clamping said needle thread, said arresting means being effective during sewing of sewing machine, and unlocking means cooperating with said arresting means for eliminating the Arrest when operating said thread catching and cutting means.
 9. The combination as claimed in claim 7, wherein said arresting means for holding said clamping face in said position behind said needle during the sewing operation of said chainstitch sewing machine, said unlocking means cooperating with said actuating means for said thread catching and cutting means for eliminating the arrest when operating said thread catching and cutting means comprising an arresting plate secured to the other arm of said double-armed lever and having a cutout with a bearing edge, a notched plate pivoted to said sewing machine and having an angled edge cooperating with said bearing edge of said arresting plate, and a downwardly angled part, a spring plate secured to the underface of said downwardly angled part of said notched plate, a spring for bearing said notched plate against said bearing edge of said arresting plate, a double armed connecting lever, one arm of which being connected with said actuating means for said thread catching and cutting means, a lug secured to the other arm of said double-armed connecting lever and cooperating with said spring plate, said looper thread clamping means including a pivoted looper thread clamping lever having a first arm for clamping said looper thread between a bearing surface and said first arm, and a second arm formed with a tongue, and a spring for holding said looper thread clamping lever in an inoperative position, actuated by said actuating means for said looper thread clamping means and consisting of an adjustable set screw inserted in said arresting plate and cooperating with said tongue of said looper thread clamping lever. 